Issue using with Stepper

[karthikgs7]

Describe the bug After couple of actions, one of the buttons got disabled, and tapping on the other button sends the invalid action to the store.

To Reproduce Try copy-pasting the code in SwiftUI file, run and do couple of actions with the stepper.

import SwiftUI
import ComposableArchitecture

struct CounterState: Equatable {
    var title: String = ""
    var count: Int = 0
}

enum CounterAction: Equatable {
    case incrementCountTapped
    case decrementCountTapped
}

struct CounterEnvironment {}

let counterReducer = Reducer<CounterState, CounterAction, CounterEnvironment> { state, action, environment in
    switch action {
    case .incrementCountTapped:
        state.count += 1
        return .none
    case .decrementCountTapped:
        state.count -= 1
        return .none
    }
}

struct CounterView: View {

    let store: Store<CounterState, CounterAction>

    var body: some View {
        WithViewStore(self.store) { viewStore in
            HStack {
                Text("Count")
                Stepper(onIncrement: {
                    viewStore.send(.incrementCountTapped)
                }, onDecrement: {
                    viewStore.send(.decrementCountTapped)
                }, label: {
                    Text("\(viewStore.count)")
                })
            }
        }
    }
}

struct ContentView: View {
    var body: some View {
        CounterView(
            store: Store(
                initialState: CounterState(),
                reducer: counterReducer,
                environment: CounterEnvironment()
            )
        )
    }
}

Expected behavior Tapping on the button should be changing the value without disabling the UI elements.

Screenshots

Environment

• Xcode 11.5
• Swift 5

[mbrandonw]

Hey @karthikgs7, thanks for the report!

We've actually stumbled upon this before, and we've gotten some confirmation from Apple that this is most likely a SwiftUI bug. We documented this on the WithViewStore type:

https://github.com/pointfreeco/swift-composable-architecture/blob/c9c1a9a50040408c436e496bac35007add327186/Sources/ComposableArchitecture/SwiftUI/WithViewStore.swift#L15-L18

To work around can you use the version of Stepper that takes a binding instead? You will need to manually check the before and after value in the reducer to determine if the value was incremented or decremented.

[mbrandonw]

Gonna close this issue for now, but please feel free to reopen if you have more questions!